Fabric press improvements



Oct. 26, 1965 D. B. WICKER 3,214,329

FABRIC PRESS IMPROVEMENTS Filed Jan. 24, 1963 2 Sheets-Sheet 1 FIG. I

T0 DRYER FIG. 2 FIG.4

Oct. 26, 1965 D. B. WICKER FABRIC PRESS IMPROVEMENTS 2 Sheets-Sheet 2 Filed Jan. 24, 1963 a i M/GC PAHKHA .3 m/ MHG mHH/G H TQM HM 8 d: H 1 Q HM @HMM/ GMM NH H G/ FIG. 6

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United States Patent 3,214,329 FABRIC PRESS IMPROVEMENTS Dan E. Wicker, Iiondonville, N.Y., assignor to Huyck Corporation, Stamford, Conn., a corporation of New York Filed Jan. 24, 1963, er. No. 253,549 Claims. (Ci. 162358) This invention relates to fabric presses of papermaking machines and more particularly to improved felts and fabrics for use in combination with fabric presses.

This invention relates more specifically to the step in which water is removed from moist, freshly formed paper sheets by running them between rotating cylindrical squeeze rolls commonly known as presses. It is the traditional practice to convey such running sheets into and through press nips by means of running endless bands comprising woven and felted textile fibers, and traditionally known as paperrnakers felts. The earliest presses used solid cylindrical rolls, and the expressed water necessarily drained through the felt and flowed counter-currently over the surface of the rotating lower roll until removed from the system by falling free therefrom. A later embodiment constituted the so-called suction press in which the roller that runs inside the felt comprises a hollow cylinder with perforations therethrough; a suction box with vacuum is utilized inside the hollow cylinder to apply vacuum to the felt and paper sheet at and adjacent the nip region. The openings in the perforated roll provide void space into which the expressed water moves momentarily while passing beyond the nip region. Under usual circumstances, most of the water is thereafter flung out of the roll by centrifugal force and is caught by a guard pan and removed from the system. Some of the water, of course, may be drawn by the vacuum within the suction box and removed through the vacuum pump.

In an improved apparatus known as a fabric press, plain rollers are used, the sheet being passed therebetween in combination with a conventional felt. In one embodiment there runs inside the felt a mat or fabric with voids therein to provide the space to receive the expressed water while it passes through and beyond the nip region. Such apparatus anticipates the water remaining in the voids of the fabric and being removed in another part of the path of travel by the action of centrifugal force. Another embodiment of the fabric press provides for the expressed water largely to pass through the voids of the fabric and be deposited as a film on the surface of the cooperating roller. A wiper or scraper thereafter removes the film from the roller such that a substantially water-free surface moves into the ingoing side of the nip.

It is evident that in both modifications of the fabric press the major consideration is provision of the necessary void space for expressed water to occupy While passing through and beyond the nip region. If such space is not provided, the squeezing action results in a backup and accumulation of excess water at the ingoing side of the nip in such a manner as to dilute the sheet and cause a disturbance or destruction of its formation in an action commonly spoken of as crushing. In the embodiment of the fabric press that anticipates the expressed water largely remaining in the fabric that runs inside the felt, it is desirable to enhance the forces that retain water within this structure. In the embodiment that provides for the Water to pass through the fabric and onto the surface of the cooperating roll, it is desirable for the fabric to retain a minimum amount of water and for a maximum amount to be transmitted to the roll surface. In all embodiments of the fabric press the provision of void volume is a major consideration, and hence, the felt pref- ICC erably should provide the void space but minimize the possible transmission of water in such space back into the sheet after passing through the emerging side of the nip. In all embodiments, it is desirable that the felt be capable of receiving water from the sheet as pressure is imposed thereon, but also be capable of easily releasing it to the fabric and through the fabric to the roller surface that runs therein. The inside fabrics or mats mentioned all are relatively incompressible in order that the void volume be preserved throughout the high pressure region of the nip. None of the fabrics or mats now in use provide a barrier to impede transfer of water through the structure and onto the surface of the inside roll. Therefore, the embodiments disclosed have the disadvantage of the structure of the foraminate band striking through the felt to emboss and imprint on the paper sheet that is pressed therewith to produce a condition commonly spoken of as marking. Furthermore, in the embodiment of the fabric press that presupposes the retention of the expressed water within the voids of the inside fabric (rather than their transfer to the surface of the inside roll) there is a disadvantage of uninhibited transfer of water entirely through the fabric to a point on the surface of the roll that does not conform to the concept of the disclosure.

Accordingly, it is an object of this invention to provide improved apparatus for removing water from a Wet paper web.

It is another object of this invention to provide felts which will retain increased amounts of water pressed from wet paper webs, and will transport the water through the nip region of press rolls to selected dewatering regions.

A further object of this invention is to provide press felts which will minimize the extent of re-wetting of a pressed paper web.

Yet another object of this invention is to pass a pair of duplex felts between press r-olls along with a wet web, the duplex felt that is adjacent to the wet web being water repellent and the duplex fabric that is adjacent to the inside roller being water receptive.

Other objects Will be apparent to those skilled in the art from reading the following description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic view of a press section of a papermaking machine;

FIGURE 2 is a schematic cross-sectional view of one embodiment of this invention taken along line 22 of FIG. 1, being two press felts as used to transport a wet paper web between press rolls;

FIGURE 3 is a schematic plan view, on an enlarged basis, of an embodiment of a duplex press felt useful in this invention;

FIGURE 4 is a cross-sectional view of the press felt along line 4-4 of FIG. 3;

FIGURE 5 is another cross-sectional view of the press felt along line 5-5 of FIG. 3;

FIGURE 6 is an enlarged, schematic, plan view of another duplex press felt useful in this invention;

FIGURE 7 is a cross-sectional view of the press. felt of FIG. 6 taken along line 7--7;

FIGURE 8 is another cross-sectional view of the press felt of FIG. 6 taken along line 8-8;

FIGURE 9 is an enlarged, schematic plan view of another press felt useful in this invention;

FIGURE 10 is a cross-sectional view of the press felt of FIG. 9 taken along line 1010;

FIGURE 11 is another cross-sectional view of the press felt of FIG. 9 taken along line 1111, and

FIGURE 12 is an enlarged, schematic cross-sectional view of another duplex press felt useful in this invention.

The objects of this invention are accomplished by the use of a fabric press in which two duplex press felts are used as a papermakers wet felt to carry a moist paper web between press rolls where water is forced from the web into the two duplex felts which then transport the water to regions where the water is removed. Each of the duplex, or two-layered, press felts has one layer of low void volume which is desirably well felted and a second layer of high void volume, which is desirably less felted. The low void volume layer may be soft or flexible, and the high void volume layer may be hard or stiff. It is preferred that the low void volume layer be highly compressible and the high void volume layer be less compressible, the degree of compressibility of the latter being sufficient to avoid marking the wet paper web. The preferred materials for the yarn of the low void volume layer are predominantly natural animal fibers, such as wool. The high void volume layer desirably contains a significant amount of synthetic polymer yarns, such as polyamides, polyesters, and the like. Desirably the synthetic yarns constitute from about to 100% of the high void volume layer, although lesser ratios may be used.

It has been found that unexpectedly improved results are obtained by using two duplex press felts arranged with the high void volume layers adjacent to each other to transport a wet paper web between press rolls. Without wishing to be bound by a theory of operation it is believed that because of the high volume and low compressibility of the high void volume layers of the duplex press felts, higher press loads may be applied without water build-up before the nip and without crushing the wet web. It is a feature of this invention that there is little tendency for the water to return from the high void volume layer into the low void volume layer, and so back into the web, after the pressure of the press roll is removed. Moreover, the void sizes in the low void volume layer are sufficiently small that retained water will not be expelled from the layer by the centrifugal forces encountered in pressing operations carried out at usual papermaking speeds. Most of the water is retained in the high void volume layer of the felts and is removed at a point beyond the press rolls by well known means such as described below.

As shown in FIG. 1, the moist paper web 2 from the web forming section (not shown) of the papermaking machine is carried by endless duplex press felts 4, 6 through press roll 8 and inside press roll 10. The pressed paper web then continues onto the drying section (not shown). Part of the expressed water passes through duplex press felts 4, 6 and is transferred to the surface of inner press roll 10 from which it may be removed by wiper, or doctor blade 11. Part of the water is retained in the felts and may be removed as the press felts 4, 6 pass compressed air supply conduits 12, 14 respectively. The water desirably is blown into receiving trays 16, 18 from which it drains. Water may also be removed as fabrics 4, 6 pass over suction boxes 20, 22 and enter the suction boxes from which it drains.

As shown in FIG. 2 felts 4 and 6 are used with high void volume layers 24, 26 adjacent to each other. Water is pressed from moist paper web 2 which may be placed in contact with low void volume layer 28 and is forced through layer 28 into high void volume layer 26 of felt 6 as the two press felts and the wet paper web pass between the press rolls. Some of the water passes into high void volume layer 24 of felt 4. The water is essentially all retained in the two layers 24, 26 of high void volume. The low void volume layers 28, 30 engaged respectively with paper web 2 and with cooperating press roll 10, hinder the water from passing out of high void volume layers 24, 26 until moist paper web 2 and felts 4, 6 have passed beyond the nip of the press rolls.

A preferred embodiment of a duplex felt useful in this invention is shown in FIGURES 3, 4 and 5. Duplex felt is made up of fine textured, low void volume layer 42 (FIG. 4) and coarse textured, high void volume layer 44 which are woven together into a unitary fabric by yarns 46. Fine layer 42 is made up of yarns 48 and 50, which comprise a 4-harness satin, or crow-foot, weave in a relatively fine, low void volume structure. The yarns 48 and 50 are of soft, low twisted construction, are easily felted and provide good cushion. In this embodiment layer 42 is preferentially disposed on the paper webcontacting side of duplex felt 6 and on the press-roll-contacting side of duplex felt 4.

Layer 44 is made up of yarns 52 and 54 which comprise a plain weave in a relatively coarse, high void volume structure. Yarns 52, 54 are of relatively incompressible construction, and if made of wool are hard twisted and are less easily felted than yarns 48, 50.

Yarns 46 stitch the two layers 42, 44 together. If yarns 46 were absent, layers 42 and 44 would come out of the loom as two entirely separate pieces. With the yarns 46 joining them, layers 42 and 44 have the character of one fabric with a fine, well felted structure with low void volume for layer 42, and a coarse, less felted high void volume structure for layer 44.

An alternate embodiment of a duplex felt useful in this invention is the 4-harness satin shown in FIGS. 6, 7 and 8. In this embodiment the duplex felt is formed of yarns 62, 64. Yarns 62 have a soft twist, a high tendency to felt and are compressible to provide cushion. Yarns 64 have a hard twist, have less tendency to felt and are less compressible. Yarns 62 are disposed predominantly adjacent to face side 61 of press felt 6t? and so contact wet paper web 2. Due to the predominant layering of yarns 62, 64, felt 60 has a fine, felted, low void volume layer on face side 61, and a coarse layer with a high void volume on rear side 63.

Another embodiment of the duplex felt useful in this invention is shown in FIGURES 9, l0 and 11. The felt is comprised of yarns in two distinct woven patterns. Yarns 72, 74 comprise a 4-harness satin, or crow-foot, weave in a relatively fine, low void volume structure. Yarns 72 are of soft, low twisted construction, are easily felted and provide cushion. Yarns 72 are preferentially disposed to face side 76 of felt 70. Yarns 74 are highly twisted, less susceptible to felting and less compressible. Yarns 74 are preferentially disposed on rear side 78 of fabric 70.

Yarns 80, 82 comprise a plain weave in a coarse, high void volume structure. Yarns 80 are similar to yarns 72 and are disposed predominantly on face side 76. Yarns 82 are similar to yarns 74 and are disposed predominantly on rear side 78. Yarns 84 comprise locking stitches inserted at regular intervals in order more firmly to interlock the two woven elements of felt 79. Without yarns 84 the two woven elements would be loosely interlocked; with the locking stitches therein, the final felt 70 has the character of one fabric with a fine, well-felted, low void volume structure disposed preferentially to face side 76 and a coarse, less felted, high void volume structure preferentially disposed to rear side 78.

Other weaves are operable in the practice of this invention, such as a S-harness or 6-harness satin, or the like, for the low void volume layer, and a basket weave, twill, broken twill, or the like for the high void volume layer. In general, any two layered felt or fabric is operable in the practice of this invention which has one layer of a fine, felted, compressible, low void volume structure and a second layer of a coarse, high void volume, less felted and less compressible structure.

Another embodiment of this invention is shown in FIGURE 12. Duplex felt desirably comprises a scrim or base fabric 92 woven in the manner described above or woven with other weaves such as a plain weave, a twill weave, a 4-harness satin, or the like. A nonwoven batt 94 formed by carding machines or garnetts may be applied to scrim 92 by the use of barbed needles which so entangle the batt with the Woven structure that there is a high degree of adhesion between the two layers. In this combination, the batt side, or face side 96 of the felt may be provided with a denser structure and lower void volume than the scrim, or rear side 98. Moreover batt side 96 may be made denser than textile structures that are made by Weaving alone. The water removal effect of the needled batt structure will be at least as great and, in most instances, may be greater than woven structures.

Although the duplex felts useful in this invention are operable in their natural state, their effectiveness may be enhanced by treating them to make them water attractive or water repellent. For instance, by treating the web contacting felt to render it water repellent the tendency of Water to return from the roll contacting felt into the web contacting felt is reduced. Thus, the re-wetting of the paper web as it emerges from the press rolls is reduced. The repellent nature of the paper contacting felt will not prevent water from being forced from the wet paper web through it by the mechanical pressure applied by the press rolls. Where it is desired that as much Water as possible be retained in the felts, their treatment to render them water receptive will increase their water retention capability.

There are various methods of rendering textile structures, including fibers, yarns and fabrics water repellent. One method comprises the application of fiuorocarbons, such as Minnesota Mining & Manufacturing Corporations compound FC-208. This compound has the chemical formula C8F17 and is a modified acrylate. It is available as a non-ionic emulsion of the fluorocarbon resin containing 28% solvent. An impregnating solution may be prepared by dissolving 0.1 part of sodium chloride or sodium acetate in 100 parts by weight of a bath. The fluorocarbon resin emulsion equal to 3.5 parts by weight of the bath is added with sufficient agitation to distribute the resin. A solution is prepared containing one part of fluorocarbon solids which is sufficient to fairly wet a fabric. Isobutanol may be added to the solution in the amount of 4% of the bath volume as a fugitive wetting agent if the fabrics do not wet out readily. The remainder of the bath is water. After the material has been thoroughly wetted, the bath solution is drained, and the material is brought to a wet pick-up of about 100% of its dry weight. The treated material is then dried and cured at 250-300 F. for five to ten minutes to provide a dry weight pick-up of about 1%. Thereafter, the resultant fabric is water repellent, has a noticeably decreased tendency to absorb Water and has an increased tendency to release or shed water.

Another method of treating textile materials to make them water repellent is to apply an organo-polysiloxane containing a zirconium or tin salt. Such a material is available under the name Cravenette SWS with catalyst 54. The latter material is an emulsion consisting of 30% by Weight of silicone solids and employing a metallic organic salt as a catalyst. The materials to be treated are immersed in a bath and extraneous material removed from it. The repellent in the amount of 5% by weight of dry material is diluted with its own volume of water and distributed throughout the bath by agitation. The catalyst in the amount of 2% by weight of the dry material is similarly diluted and added to the bath. The pH of the bath varies between about 2.5 and 7. The material is retained in the bath for 30 minutes or until the milky appearance caused by the repellent disappears and is then removed and dried. No thermal cure is required because the resin cures at room temperature. A dry weight pick-up of about 1% is obtained and will produce the water repellent properties desired.

Another type of water repellent treatment for textile materials comprises the application of stearamido-methylpyridiniurn chloride. A representative bath is prepared by dispersing at 130-140 F. an amount of the compounds equivalent to 6% of the weight of the bath, using an amount of solvent equivalent to 30% of thefinal bath volume. The bath is continuously stirred and diluted to the desired volume with water. Sodium acetate in the amount of 10% of the Weight of the compound added is dissolved separately in water and added to the bath. The final bath temperature should be about F. A sufficient amount of liquid is added to cause a wet weight pick-up of 60% of the dry weight of the material. After the material is dried it is cured at 300 F. for two minutes to provide a final dry weight pick-up of about 4%. The resultant fabric will thereafter show water repellent properties.

Other methods of treating textile materials to render them water repellent involve the application of such material as Atcodri Z which is a mixture of a zirconium salt and a paraffin Wax. The Zirconium salt may be zirconium stearate.

Still another method of making textile materials water repellent is to apply thermo-setting resins, such as Phobotex FTC along with a catalyst.

A method for treating textile materials to render them more water receptive comprises the application of an anionic exchange resin containing polyoxyethyl chains and ionic groups. Such a material is available under the name Aston 108 from Onyx Oil & Chemical Company. It is applied to the material in the form of soluble polymers containing reactive groups together with soluble multifunctional cross-linking agents. The reaction is carried out at elevated temperatures up to about 212 F. A solution containing 2 5% of Aston 108, a cross-linking agent in the ratio of 7:3 to the Aston 108, and about 0.5% of an aromatic polyglycol ether, such as Neutronyx 600 is applied to the material. Thereafter the material is dried and cured with infra-red radiation at as high a temperature as it will withstand without damage thereto, but in any event at 212 F. or higher.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. For instance, while the invention has been described for use with wet paper webs in papermaking processes, it is applicable as well to other absorbent materials in related processes.

What is claimed is:

1. A papermakers wet felt means for use in the press roll section of a papermaking machine which comprises first and second Woven felts, each of said felts being formed of first yarns that are relatively hard twisted to provide stiffness and being relatively difiicult to felt and second yarns that are relatively soft twisted, more flexible than said first yarns and having a high tendency to felt, said first yarns being disposed to a substantially greater extent at one side of each of said felts than the other side thereof and forming a relatively high void volume layer, said high void volume side of said first felt being in contact with said high void volume side of said second felt, and said second yarns being felted and being disposed to a substantially greater extent at said other side than at said high void volume side of said felts and forming a relatively low void volume layer, said layers being of relatively high void volume and relatively low void volume with respect to each other.

2. An improved fabric press for removing increased amounts of water from a wet web of paper and similar absorbent structure in the papermaking and related industries comprising a pair of cooperating press rolls, and means to transport the wet Web between said press rolls comprising first and second duplex felts, each of said duplex felts comprising a felted, compressible, relatively low void volume first layer and a less felted, less compressible, relatively high void volume second layer, said void volumes being respectively low and high relative to each other, said second layer of said first felt being in contact with said second layer of said second felt, and one of said first layers being in contact with the wet web, whereby water pressed from said wet web through said first layer of said first felt passes into said second layers of said first and second felts and is retained therein.

3. A fabric press as defined in claim 2 wherein the wet web contacting felt is water repellent.

4. A fabric press according to claim 2 wherein the wet web contacting felt is water repellent and the other felt is water receptive.

5. A fabric press according to claim 2 wherein first and second duplex felts are water receptive.

References Cited by the Examiner UNITED STATES PATENTS 1,651,476 12/27 Sheehan 139-383 2,821,771 2/58 Skeer 139-383 2,949,134 8/60 Hindle et al. 139383 3,093,535 6/63 Brauns et a1 162358 FOREIGN PATENTS References Gated by the Applicant UNITED STATES PATENTS Walsh et al. Millspaugh. Barstow. Brodin. Gates. Holden et al.

FOREIGN PATENTS Canada. Germany.

DONALD W. PARKER, Primary Examiner. 

2. AN IMPROVED FABRIC PRESS FOR REMOVING INCREASED AMOUNTS OF WATER FROM A WET WEB OF PAPER AND SIMILAR ABSORBENT STURCTURE IN THE PAPERMAKING AND RELATED INDUSTRIES COMPRISING A PAIR OF COOPERATING PRESS ROLLS, AND MEANS TO TRANSPORT THE WET WEB BETWEEN SAID PRESS ROLLS COMPRISING FIRST AND SECOND DUPLEX FELTS, EACH OF SAID DUPLEX FELTS COMPRISING A FELTED, COMPRESSIBLE, RELATIVELY LOW VOID VOLUME FIRST LAYER AND A LESS FELTED, LESS COMPRESSIBLE, RELATIVELY HIGH VOID VOLUME SECOND LAYER, SAID VOID VOLUMES BEING RESPECTIVELY LOW AND HIGH RELATIVE TO EACH OTHER, SAID SECOND LAYER OF SAID FIRST FELT BEING IN CONTACT WITH SAID SECOND LAYER OF SAID SECOND FELT, AND ONE OF SAID FIRST LAYERS BEING IN CONTACT WITH THE WET WEB, WHEREBY WATER PRESSED FROM SAID WET WEB THROUGH SAID FIRST LAYER OF SAID FIRST FELT PASSES INTO SAID SECOND LAYERS OF SAID FIRST AND SECOND FELTS AND IS RETAINED THEREIN. 